In the summer, I tested ten ebook reader apps for Android, looking for something that worked well with large documents. My best choices were Moon+ and Mantano, but neither was ideal. Moon+ took 20 seconds to open the Summa epub, though it searched it in a speedy 20 seconds, and Mantano opened it almost instantly, though it took 80 seconds to search.
The Moon+ developer has just pointed me to his latest apk of Moon+ which improves the Moon+ loading speed significantly It can now load the Summa in 10 seconds on my Archos 43, and probably faster on faster devices. The search seems to be slightly slowed down, to about 23 seconds, but that's still quite decent. Moon+ is now clearly the best reader for large documents if you want searching, and is all-around an excellent reader. So I think I'm close to the point where I can start converting my large library from Plucker to epub.
I've accordingly updated my mini-reviews of epub readers.
Further update: On my new Epic 4G Touch (the Sprint version of the Galaxy S2, though a bit slower), it takes 4 seconds for the latest Moon+ to open the Summa, and 25 to search.